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linux-next/net
Mauricio Faria de Oliveira bd961c9bc6 rtnetlink: fix rtnl_fdb_dump() for ndmsg header
Currently, rtnl_fdb_dump() assumes the family header is 'struct ifinfomsg',
which is not always true -- 'struct ndmsg' is used by iproute2 ('ip neigh').

The problem is, the function bails out early if nlmsg_parse() fails, which
does occur for iproute2 usage of 'struct ndmsg' because the payload length
is shorter than the family header alone (as 'struct ifinfomsg' is assumed).

This breaks backward compatibility with userspace -- nothing is sent back.

Some examples with iproute2 and netlink library for go [1]:

 1) $ bridge fdb show
    33:33:00:00:00:01 dev ens3 self permanent
    01:00:5e:00:00:01 dev ens3 self permanent
    33:33:ff:15:98:30 dev ens3 self permanent

      This one works, as it uses 'struct ifinfomsg'.

      fdb_show() @ iproute2/bridge/fdb.c
        """
        .n.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg)),
        ...
        if (rtnl_dump_request(&rth, RTM_GETNEIGH, [...]
        """

 2) $ ip --family bridge neigh
    RTNETLINK answers: Invalid argument
    Dump terminated

      This one fails, as it uses 'struct ndmsg'.

      do_show_or_flush() @ iproute2/ip/ipneigh.c
        """
        .n.nlmsg_type = RTM_GETNEIGH,
        .n.nlmsg_len = NLMSG_LENGTH(sizeof(struct ndmsg)),
        """

 3) $ ./neighlist
    < no output >

      This one fails, as it uses 'struct ndmsg'-based.

      neighList() @ netlink/neigh_linux.go
        """
        req := h.newNetlinkRequest(unix.RTM_GETNEIGH, [...]
        msg := Ndmsg{
        """

The actual breakage was introduced by commit 0ff50e83b5 ("net: rtnetlink:
bail out from rtnl_fdb_dump() on parse error"), because nlmsg_parse() fails
if the payload length (with the _actual_ family header) is less than the
family header length alone (which is assumed, in parameter 'hdrlen').
This is true in the examples above with struct ndmsg, with size and payload
length shorter than struct ifinfomsg.

However, that commit just intends to fix something under the assumption the
family header is indeed an 'struct ifinfomsg' - by preventing access to the
payload as such (via 'ifm' pointer) if the payload length is not sufficient
to actually contain it.

The assumption was introduced by commit 5e6d243587 ("bridge: netlink dump
interface at par with brctl"), to support iproute2's 'bridge fdb' command
(not 'ip neigh') which indeed uses 'struct ifinfomsg', thus is not broken.

So, in order to unbreak the 'struct ndmsg' family headers and still allow
'struct ifinfomsg' to continue to work, check for the known message sizes
used with 'struct ndmsg' in iproute2 (with zero or one attribute which is
not used in this function anyway) then do not parse the data as ifinfomsg.

Same examples with this patch applied (or revert/before the original fix):

    $ bridge fdb show
    33:33:00:00:00:01 dev ens3 self permanent
    01:00:5e:00:00:01 dev ens3 self permanent
    33:33:ff:15:98:30 dev ens3 self permanent

    $ ip --family bridge neigh
    dev ens3 lladdr 33:33:00:00:00:01 PERMANENT
    dev ens3 lladdr 01:00:5e:00:00:01 PERMANENT
    dev ens3 lladdr 33:33:ff:15:98:30 PERMANENT

    $ ./neighlist
    netlink.Neigh{LinkIndex:2, Family:7, State:128, Type:0, Flags:2, IP:net.IP(nil), HardwareAddr:net.HardwareAddr{0x33, 0x33, 0x0, 0x0, 0x0, 0x1}, LLIPAddr:net.IP(nil), Vlan:0, VNI:0}
    netlink.Neigh{LinkIndex:2, Family:7, State:128, Type:0, Flags:2, IP:net.IP(nil), HardwareAddr:net.HardwareAddr{0x1, 0x0, 0x5e, 0x0, 0x0, 0x1}, LLIPAddr:net.IP(nil), Vlan:0, VNI:0}
    netlink.Neigh{LinkIndex:2, Family:7, State:128, Type:0, Flags:2, IP:net.IP(nil), HardwareAddr:net.HardwareAddr{0x33, 0x33, 0xff, 0x15, 0x98, 0x30}, LLIPAddr:net.IP(nil), Vlan:0, VNI:0}

Tested on mainline (v4.19-rc6) and net-next (3bd09b05b0).

References:

[1] netlink library for go (test-case)
    https://github.com/vishvananda/netlink

    $ cat ~/go/src/neighlist/main.go
    package main
    import ("fmt"; "syscall"; "github.com/vishvananda/netlink")
    func main() {
        neighs, _ := netlink.NeighList(0, syscall.AF_BRIDGE)
        for _, neigh := range neighs { fmt.Printf("%#v\n", neigh) }
    }

    $ export GOPATH=~/go
    $ go get github.com/vishvananda/netlink
    $ go build neighlist
    $ ~/go/src/neighlist/neighlist

Thanks to David Ahern for suggestions to improve this patch.

Fixes: 0ff50e83b5 ("net: rtnetlink: bail out from rtnl_fdb_dump() on parse error")
Fixes: 5e6d243587 ("bridge: netlink dump interface at par with brctl")
Reported-by: Aidan Obley <aobley@pivotal.io>
Signed-off-by: Mauricio Faria de Oliveira <mfo@canonical.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2018-10-05 14:21:42 -07:00
..
6lowpan 6lowpan: iphc: reset mac_header after decompress to fix panic 2018-07-06 12:32:12 +02:00
9p Pull request for inclusion in 4.19, take two 2018-08-17 17:27:58 -07:00
802
8021q net: remove blank lines at end of file 2018-07-24 14:10:43 -07:00
appletalk Revert changes to convert to ->poll_mask() and aio IOCB_CMD_POLL 2018-06-28 10:40:47 -07:00
atm Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2018-08-15 15:04:25 -07:00
ax25 ax25: remove blank line at EOF 2018-07-24 14:10:42 -07:00
batman-adv batman-adv: Increase version number to 2018.3 2018-09-14 17:59:20 +02:00
bluetooth Bluetooth: SMP: fix crash in unpairing 2018-09-26 12:39:32 +03:00
bpf bpf/test_run: support cgroup local storage 2018-08-03 00:47:32 +02:00
bpfilter net: bpfilter: Fix type cast and pointer warnings 2018-10-05 11:51:06 -07:00
bridge netfilter: bridge: Don't sabotage nf_hook calls from an l3mdev 2018-09-20 18:24:14 +02:00
caif net: simplify sock_poll_wait 2018-07-30 09:10:25 -07:00
can Revert changes to convert to ->poll_mask() and aio IOCB_CMD_POLL 2018-06-28 10:40:47 -07:00
ceph crush: fix using plain integer as NULL warning 2018-08-13 17:55:44 +02:00
core rtnetlink: fix rtnl_fdb_dump() for ndmsg header 2018-10-05 14:21:42 -07:00
dcb net: dcb: Add priority-to-DSCP map getters 2018-07-27 13:17:50 -07:00
dccp inet: make sure to grab rcu_read_lock before using ireq->ireq_opt 2018-10-02 15:52:12 -07:00
decnet decnet: fix using plain integer as NULL warning 2018-08-09 14:11:24 -07:00
dns_resolver net: remove blank lines at end of file 2018-07-24 14:10:43 -07:00
dsa net: dsa: Drop GPIO includes 2018-08-27 15:24:33 -07:00
ethernet net: Convert GRO SKB handling to list_head. 2018-06-26 11:33:04 +09:00
hsr
ieee802154 net: ieee802154: 6lowpan: remove redundant pointers 'fq' and 'net' 2018-08-06 11:21:15 +02:00
ife net: sched: ife: check on metadata length 2018-04-22 21:12:00 -04:00
ipv4 ipv4: fix use-after-free in ip_cmsg_recv_dstaddr() 2018-10-02 22:32:05 -07:00
ipv6 Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/klassert/ipsec 2018-10-01 22:29:25 -07:00
iucv net/iucv: declare iucv_path_table_empty() as static 2018-09-05 22:32:22 -07:00
kcm Revert "kcm: remove any offset before parsing messages" 2018-09-17 18:43:42 -07:00
key Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/klassert/ipsec-next 2018-07-27 09:33:37 -07:00
l2tp l2tp: fix unused function warning 2018-08-13 20:45:49 -07:00
l3mdev
lapb
llc Merge ra.kernel.org:/pub/scm/linux/kernel/git/davem/net 2018-08-09 11:52:36 -07:00
mac80211 mac80211: fix setting IEEE80211_KEY_FLAG_RX_MGMT for AP mode keys 2018-10-01 09:13:48 +02:00
mac802154 net: mac802154: tx: expand tailroom if necessary 2018-08-06 11:21:37 +02:00
mpls mpls: allow routes on ip6gre devices 2018-09-24 12:19:27 -07:00
ncsi net/ncsi: Fixup .dumpit message flags and ID check in Netlink handler 2018-08-22 21:39:08 -07:00
netfilter netfilter: xt_socket: check sk before checking for netns. 2018-09-28 14:47:41 +02:00
netlabel netlabel: check for IPV4MASK in addrinfo_get 2018-09-21 18:58:34 -07:00
netlink Merge ra.kernel.org:/pub/scm/linux/kernel/git/davem/net 2018-08-05 13:04:31 -07:00
netrom Revert changes to convert to ->poll_mask() and aio IOCB_CMD_POLL 2018-06-28 10:40:47 -07:00
nfc NFC: Fix possible memory corruption when handling SHDLC I-Frame commands 2018-09-18 19:55:01 -07:00
nsh nsh: set mac len based on inner packet 2018-07-12 16:55:29 -07:00
openvswitch openvswitch: load NAT helper 2018-10-04 21:45:16 -07:00
packet net/packet: fix packet drop as of virtio gso 2018-10-04 22:23:15 -07:00
phonet Revert changes to convert to ->poll_mask() and aio IOCB_CMD_POLL 2018-06-28 10:40:47 -07:00
psample
qrtr net: qrtr: Reset the node and port ID of broadcast messages 2018-07-05 20:20:03 +09:00
rds rds: Fix build regression. 2018-09-23 12:25:15 -07:00
rfkill Here are quite a large number of fixes, notably: 2018-09-03 22:12:02 -07:00
rose Revert changes to convert to ->poll_mask() and aio IOCB_CMD_POLL 2018-06-28 10:40:47 -07:00
rxrpc rxrpc: Fix error distribution 2018-09-28 10:33:17 +01:00
sched net: sched: act_ipt: check for underflow in __tcf_ipt_init() 2018-10-01 22:34:14 -07:00
sctp sctp: fix fall-through annotation 2018-10-03 09:33:13 -07:00
smc smc: generic netlink family should be __ro_after_init 2018-09-20 07:49:55 -07:00
strparser strparser: remove redundant variable 'rd_desc' 2018-08-01 10:00:06 -07:00
sunrpc NFS client updates for Linux 4.19 2018-08-23 16:03:58 -07:00
switchdev
tipc tipc: ignore STATE_MSG on wrong link session 2018-10-01 22:35:30 -07:00
tls tls: fix currently broken MSG_PEEK behavior 2018-09-17 08:03:09 -07:00
unix af_unix: ensure POLLOUT on remote close() for connected dgram socket 2018-08-03 16:44:19 -07:00
vmw_vsock vsock: split dwork to avoid reinitializations 2018-08-07 12:39:13 -07:00
wimax wimax: remove blank lines at EOF 2018-07-24 14:10:42 -07:00
wireless cfg80211: fix use-after-free in reg_process_hint() 2018-10-01 09:14:03 +02:00
x25 x25: remove blank lines at EOF 2018-07-24 14:10:42 -07:00
xdp xsk: fix return value of xdp_umem_assign_dev() 2018-08-21 22:06:53 +02:00
xfrm Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/klassert/ipsec 2018-10-01 22:29:25 -07:00
compat.c net: avoid unnecessary sock_flag() check when enable timestamp 2018-08-06 10:42:48 -07:00
Kconfig net: remove blank lines at end of file 2018-07-24 14:10:43 -07:00
Makefile bpfilter: check compiler capability in Kconfig 2018-06-28 13:36:39 +09:00
socket.c socket: fix struct ifreq size in compat ioctl 2018-09-13 16:01:06 -07:00
sysctl_net.c